On Thu, Nov 01, 2018 at 03:40:35PM -0700, Daniel Verkamp wrote: > From: Changpeng Liu <changpeng.liu@xxxxxxxxx> > > In commit 88c85538, "virtio-blk: add discard and write zeroes features > to specification" (https://github.com/oasis-tcs/virtio-spec), the virtio > block specification has been extended to add VIRTIO_BLK_T_DISCARD and > VIRTIO_BLK_T_WRITE_ZEROES commands. This patch enables support for > discard and write zeroes in the virtio-blk driver when the device > advertises the corresponding features, VIRTIO_BLK_F_DISCARD and > VIRTIO_BLK_F_WRITE_ZEROES. > > Signed-off-by: Changpeng Liu <changpeng.liu@xxxxxxxxx> > Signed-off-by: Daniel Verkamp <dverkamp@xxxxxxxxxxxx> > --- > dverkamp: I've picked up this patch and made a few minor changes (as > listed below); most notably, I changed the kmalloc back to GFP_ATOMIC, > since it can be called from a context where sleeping is not allowed. > To prevent large allocations, I've also clamped the maximum number of > discard segments to 256; this results in a 4K allocation and should be > plenty of descriptors for most use cases. > > I also removed most of the description from the commit message, since it > was duplicating the comments from virtio_blk.h and quoting parts of the > spec without adding any extra information. I have tested this iteration > of the patch using crosvm with modifications to enable the new features: > https://chromium.googlesource.com/chromiumos/platform/crosvm/ > > v9 fixes a number of review issues; I didn't attempt to optimize the > single-element write zeroes case, so it still does an allocation per > request (I did not see any easy place to put the payload that would > avoid the allocation). > > CHANGELOG: > v9: [dverkamp] fix LE types in discard struct; cleanups from Ming Lei > v8: [dverkamp] replace shifts by 9 with SECTOR_SHIFT constant > v7: [dverkamp] use GFP_ATOMIC for allocation that may not sleep; clarify > descriptor flags field; comment wording cleanups. > v6: don't set T_OUT bit to discard and write zeroes commands. > v5: use new block layer API: blk_queue_flag_set. > v4: several optimizations based on MST's comments, remove bit field > usage for command descriptor. > v3: define the virtio-blk protocol to add discard and write zeroes > support, first version implementation based on proposed specification. > v2: add write zeroes command support. > v1: initial proposal implementation for discard command. > --- > drivers/block/virtio_blk.c | 83 ++++++++++++++++++++++++++++++++- > include/uapi/linux/virtio_blk.h | 54 +++++++++++++++++++++ > 2 files changed, 135 insertions(+), 2 deletions(-) Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
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